Server systems may be mounted in racks or enclosures, each rack holding a plurality of individual servers or blades. A server may be relatively powerful computer, which may comprise multiple microprocessors, that may be adapted for coupling together multiple personal computers and provide remote processing functionality. Servers may be used for mission-critical services such as on-line banking, on-line shopping and the like, and each rack of servers may have multiple power supplies, these power supplies may create a fully redundant power supply system. A fully redundant power supply system may have two or more power supplies, any one of which may be capable of supplying power for the entire rack of servers. Thus, if one power supply fails, the remaining power supply or power supplies may have the capability of supplying the necessary power while the failed power supply is replaced.
To balance load, each power supply in a redundant configuration may have a load share signal that may couple to a load sharing line coupled between power supplies. Each power supply may be designed and configured to drive the line to a voltage proportional to its output current (power). Each power supply may monitor the load sharing line and attempt to raise or lower its output current to match the voltage on the load share line. In this way, the load may be shared between the two or more power supplies.
However, there may be a need to verify that sufficient power is available, or redundancy of supplied power may be maintained, prior to allowing an additional device, such as a server, installed in the rack to power-on.